1. Field of the Invention
The present invention relates to a back light module, and more specifically, to a back light module for preventing light bleed-through phenomenon.
2. Description of the Prior Art
Backlight units are known in the art. The backlight unit, which is a key element in the fabrication of liquid crystal displays, is widely used in digital cameras, PDAs, vehicle satellite navigation systems, computer monitors, flat panel TVs and so on. Typically, a backlight unit, which is generally installed underneath a display panel, comprises a light source (or multiple light sources) and a light diffusion means for providing users and consumers with diffused, ample, and comfortable backlighting. Light penetrates the overlying display panel and forms various images controlled by pixel electrodes densely arranged on the display panel. Backlight units are typically divided into two major categories: edge light type and direct-type, wherein the direct-type backlight unit can provide higher intensity of light and is thus more suited for large size display panels, such as display panels or TV panels, than the edge light type.
Please refer to FIG. 1 of a cross-sectional view of a back light module 10 according to the prior art. As shown in FIG. 1, the back light module 10 is disposed under a display panel 12 and comprises at least one light source generator 14, a diffusing plate 16 disposed between the light source generator 14 and the display panel 12, a light guide plate (LGP) 18 disposed between the light source generator 14 and the diffusing plate 16, and a reflecting sheet 20 disposed under the light source generator 14 and fixed on a housing 22.
The light source generator 14 is utilized for providing a light source, and the reflecting sheet is utilized for upwardly reflecting the light source generated by the light source generator 14 and thereby increase the light use efficiency of the back light module 10. The light guide plate 18 is utilized for scattering the light source to the diffusing plate 16, and the diffusing plate 16 is employed for further scattering the light source to the display panel 12. The housing 22 disposed under the reflecting sheet 20 is utilized to assemble the diffusing plate 16, the light guide plate 18, the reflecting sheet 20 and the light source generator 14. In addition, the diffusing plate 16 further comprises at least one prism 24 disposed on a surface of the diffusing plate 16 to reduce the difference of the luminous intensities on the display panel 12 in advance. The quantity and placing order of the prism 24 employed are defined by the specification of the back light module 10.
Generally, the light source generator 14 is a cold cathode fluorescent lamp (CCFL), and the plurality of the light source generator 14 is arranged in parallel. As technologies progress, the brightness of the light source generators 14 turns to be higher and higher due to market demand. However, the improved brightness of the light source generator 14 frequently causes light gratings appeared on the display panel 12, leading to the unbalanced brightness of the display panel 12, which is called a light bleed-through phenomenon. Moreover, this light bleed-through phenomenon would cause defective display function of the display panel 12 under the long-time operation of the back light module 10, making the back light module 10 a less-competitive product.
It is therefore a primary object of the present invention to provide a back light module to prevent the defective function of the back light module caused by the light bleed-through phenomenon described in the prior art.
According to the claimed invention, the back light module is disposed under a display panel and comprises a diffusing plate, at least one light source generator, a prism, a light guide plate (LGP), at least one light shading sheet, and a reflecting sheet. The light source generator is utilized for generating a light source, and the diffusing plate is disposed between the light source generator and the display panel. The prism is disposed on a surface of the diffusing plate, and the light guide plate is disposed between the light source generator and the diffusing plate. The light guide plate is utilized for scattering the light source to the diffusing plate, and the diffusing plate is utilized for scattering the light source to the display panel. The reflecting sheet is disposed under the light source generator and is utilized for upwardly reflecting the light source to the light guide plate. The light shading sheet is a semi-transparent sheet disposed between the light source generator and the light guide plate and comprises a plurality of light holes.
It is an advantage of the present invention against the prior art that the light source in the present invention is generated by the light source generator and then scattered through a plurality of light holes of the light shading sheet to the light guide plate, assuring an uniform brightness of the scattered light source and thus preventing the light bleed-through phenomenon. Alternatively, the light holes can be neglected in case that the light shading sheet is composed of a semi-transparent sheet for the simplification of the manufacturing processes of the back light module. Consequently, the display quality of the back light module is assured by the use of the light shading sheet, making the back light module a more competitive product.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the multiple figures and drawings.